Stabilization of Si microwire arrays for solar-driven H2O oxidation to O2(g) in 1.0 M KOH(aq) using conformal coatings of amorphous TiO2

Abstract

Conductive, amorphous TiO₂ coatings deposited by atomic-layer deposition, in combination with a sputter deposited NiCrO_x oxygen-evolution catalyst, have been used to protect Si microwire arrays from passivation or corrosion in contact with aqueous electrolytes. Coated np⁺-Si/TiO₂/NiCrO_x as well as heterojunction n-Si/TiO₂/NiCrO_x Si microwire-array photoanodes exhibited stable photoelectrochemical operation in aqueous ferri-/ferro-cyanide solutions. The coatings also allowed for photoanodic water oxidation in 1.0 M KOH(aq) solutions for >2200 h of continuous operation under simulated 1 Sun conditions with ∼100% Faradaic efficiency for the evolution of O₂(g).